MUCH has been written over the past years on the effect of microwave radiation on body tissues and animals, but most of the experiments reported have been concerned with the production of heat and its associated behavioural and physiological effects1–4. There are very few references to ‘athermal’ effects such as muscular disturbances5 and disorientation—phenomena which have not attracted the scientific attention that they merit. In fact, there appears to have evolved a body of opinion dismissing the existence of any effect other than a thermal one on the pretext stated in one report4 that the photon energy in the frequency band of microwave radiation is insufficient by several orders of magnitude to produce ionization. Apparently no consideration has been given to the effect of induced electrical currents on the activity of the nervous system of an animal. Animal tissues absorb microwave radiation diffusely and since such tissues contain membrane interfaces which are semi-conducting, polarization can occur. If the microwave radiation is in pulsed form, the induced electrical currents will be modulated at the frequency of pulse repetition. It has been demonstrated experimentally that nerve conduction characteristics undergo a profound change when the nerve is subjected to a.c. excitation6. Therefore, it is to be expected that microwave radiation would have an effect on the nervous system of an animal depending on the depth of penetration.